STUDY DESIGN Proof of concept, interventional, monocentric, randomised, double blind, cross-over study: The effects of L-lysine on corticosteroid secretion will be compared to those of a placebo. STUDY OBJECTIVES Main objective: to verify that adrenal corticosteroid secretion is actually controlled by L-lysine. Secondary objective: to determine the physiological conditions that involve the control of adrenocortical function by t5-HT4 receptors. NUMBER OF SUBJECTS 20 healthy volunteers ELIGIBILITY CRITERIA (see below) DURATION OF STUDY Overall duration: 13 months Inclusion period: 12 months Follow up period (for 1 subject): 5 weeks Exclusion period: 1 month ENDPOINTS PRIMARY ENDPOINT: blood aldosterone variation during orthostatic test SECONDARY ENDPOINTS Basal aldosterone alteration Aldosterone variation during metoclopramide & salt-free diet tests Basal and stimulated (3 different tests) alterations of renin, cortisol & ACTH REGULATORY AUTHORIZATIONS Ethics committee authorization: jan 21,2010 Regulatory authorization: july 9th 2010